This invention relates to the field of machine vision, and more specifically to a method and apparatus of obtaining two- and three-dimensional inspection data for manufactured parts (such as electronic parts) in a manufacturing environment.
There is a widespread need for inspection data for electronic parts in a manufacturing environment. One common inspection method uses a video camera to acquire two-dimensional images of a device-under-test.
Height distribution of a surface can be obtained by projecting a light stripe pattern onto the surface and then reimaging the light pattern that appears on the surface. One technique for extracting this information based on taking multiple images (3 or more) of the light pattern that appears on the surface while shifting the position (phase) of the projected light stripe pattern is referred to as phase shifting interferometry, as disclosed in U.S. Pat. Nos. 4,641,972 and 4,212,073 (incorporated herein by reference).
The multiple images are usually taken using a CCD (charge-coupled device) video camera with the images being digitized and transferred to a computer where phase-shift analysis, based on images being used as xe2x80x9cbuckets,xe2x80x9d converts the information to a contour map (i.e., a three-dimensional representation) of the surface.
The techniques used to obtain the multiple images are based on methods that keep the camera and viewed surface stationary with respect to each other while moving the projected pattern.
One technique for capturing just one bucket image using a line scan camera is described in U.S. Pat. No. 4,965,665 (incorporated herein by reference).
U.S. Pat. Nos. 5,398,113 and 5,355,221 (incorporated herein by reference) disclose white-light interferometry systems which profile surfaces of objects.
In U.S. Pat. No. 5,636,025 (incorporated herein by reference), an optical measuring system is disclosed which includes a light source, gratings, lenses, and camera. A mechanical translation device moves one of the gratings in a plane parallel to a reference surface to effect a phase shift of a projected image of the grating on the contoured surface to be measured. A second mechanical translation device moves one of the lenses to effect a change in the contour interval. A first phase of the points on the contoured surface is taken, via a four-bucket algorithm, at a first contour interval. A second phase of the points is taken at a second contour interval. A control system, including a computer, determines a coarse measurement using the difference between the first and second phases. The control system further determines a fine measurement using either the first or second phase. The displacement or distance, relative to the reference plane, of each point is determined, via the control system, using the fine and coarse measurements.
Current vision inspection systems have many problems. Among the problems are assorted problems associated with the mechanical translation devices used with the vision inspection systems to handle the devices under inspection. One problem is that vision systems typically take up a large amount of linear space on a manufacturing line. Typically small devices, such as electronic chips, are placed in standard trays (called JEDEC trays), to facilitate the handling of the small devices. The JEDEC trays are rectangular in shape and when placed on a conveyor, the trays travel in a direction parallel to the longest direction of the tray. In other words, the length of the conveyor of current inspection stations is long since multiple trays being inspected at multiple stations are placed so that the short dimension of the tray is near an adjacent tray. As a result, the length of the station for inspection is relatively large.
Another problem with current vision inspection systems is that the JEDEC trays are placed on the conveyor from the top. In other words, the trays of parts are dropped down onto the conveyor of the machine vision system. This requires an additional station. At the first station, the JEDEC trays are dropped onto the line. The extra station is required since the vision systems are typically positioned on gurneys above the JEDEC trays. In other words, the length of the machine vision system station for inspecting parts is even greater since one additional station is placed on the conveyor so that the parts can be loaded to a prestaging area and then into the first vision inspection station.
Still another problem is that most current vision systems do not have a method for automatically producing a tray of all good parts and trays of rejected parts. Most current vision systems identify parts that are bad. Some include a picker that removes the bad parts from the tray. There does not appear to be a method for removing all the bad components from a tray and replacing them with good parts that previously passed inspection. In addition, there does not appear to be a method in which a tray of bad parts is produced.
Still another problem is a lack of versatility in some inspection systems. For example, most require synchronous 2D and 3D inspection of parts. Most do not allow for asynchronous inspection of parts.
To overcome the problems stated above as well as other problems, there is a need for an improved machine-vision system and more specifically for a mechanical apparatus and method for using the same that has a shorter linear footprint on a manufacturing line and one that eliminates a prestaging area for xe2x80x9cdroppingxe2x80x9d the parts to be inspected onto the line. In addition, there is a need for method and apparatus that produces trays of completely good parts and completely bad parts. There is also a need to place these parts in separate areas to prevent bad parts from mistakenly being taken as good parts. There is also a need for a more versatile inspection station that allows for asynchronous 2D inspection and 3D inspection of parts or devices in a JEDEC tray. Furthermore, there is a need for a mechanical system that allows for automated, high-speed, three-dimensional inspection of objects.
In the context of a machine-vision system for inspecting a part, this invention includes method and apparatus to provide high-speed 2D imaging of the part using interleaved scanning onto spaced-apart linear imaging rows. One embodiment uses 3 rows of CCD imaging pixels having an 8-pixel center-to-center spacing. As the imager is scanned across the part, a strobe pulse acquires 3 lines of pixels simultaneously, the imager is moved a 3-pixel distance, and the next 3 lines of pixels are acquired. Optionally, the same apparatus is used to alternately perform a 2D scan and then a 3D scan in an interleaved fashion. One such method includes scanning the device within unpatterned light to obtain a high-speed interleaved 2D image, and then scanning the device again with sine-wave spatial-modulation patterned light, and receiving image information to derive 3D height information.
FIG. 1 shows an embodiment of the present invention, a system 100 for the manufacture and inspection of devices.
FIG. 2 shows an embodiment of the present invention, a computer controlled system 200 for the control of the imaging operation and measurement functions of system 100.
FIG. 3 shows an overview of scanning head 401.
FIG. 4A shows one embodiment of a machine-vision head 401 for inspecting a device 99.
FIG. 4B shows another embodiment of a machine-vision head 401.
FIG. 4C shows yet another embodiment of a machine-vision head 401.
FIG. 4D shows still another embodiment of a machine-vision head 401.
FIG. 4E shows a projection pattern element 412 having a density pattern 472 that is a sine-wave in one direction.
FIG. 4F shows a projection pattern element 412xe2x80x2 of another embodiment, and represents a square-wave pattern near the element.
FIG. 4G shows a projection pattern element 412xe2x80x3 of another embodiment, and represents a square-wave pattern near the element.
FIG. 4H shows a projection pattern element 412xe2x80x3 of another embodiment, and represents a square-wave pattern near the element.
FIG. 4I shows yet another embodiment of a machine-vision head 401.
FIG. 5A shows a solder ball 97, illustrating the various illuminated and imagable regions.
FIG. 5B is a representation of light gathered by a non-telecentric lens 420.
FIG. 5C is a representation of light gathered by a telecentric lens 420.
FIG. 6 shows machine-vision system 600 that represents another embodiment of the present invention having more than one projector in a scanning head.
FIG. 7 shows machine-vision system 700 that represents another embodiment of the present invention having more than one imager in a scanning head.
FIG. 8 shows machine-vision system 800 that represents another embodiment of the present invention having more than one projector and more than one imager in a scanning head.
FIG. 9A shows a sensor 904A having a beamsplitter 820A.
FIG. 9B shows a sensor 904B having a beamsplitter 820B.
FIG. 9C shows a sensor 904C having a beamsplitter 820C.
FIG. 10 shows a modular machine-vision system 1000 of one embodiment of the present invention.
FIG. 11 shows a computation and comparison system 1100 of one embodiment of the present invention.
FIG. 12 is a schematic layout of another preferred embodiment of the vision system.
FIG. 13A is a schematic view of one preferred embodiment of a light intensity controller.
FIG. 13B is a schematic view of another preferred embodiment of a light intensity controller.
FIG. 13C is a schematic view of one preferred embodiment of a light intensity controller.
FIG. 14A is a schematic view of the imaging system having a memory device associated with the trilinear array.
FIG. 14B is a table lookup which is housed within memory and used to apply correction values to the values associated with the pixels of a trilinear array.
FIG. 14C is a schematic view of the imaging system having a memory device associated with the trilinear array in which a value associated with the intensity of the light is used to correct the values in memory.
FIG. 15 is a schematic view of the trilinear array with a thermoelectric cooling element associated therewith.
FIG. 16 is a perspective view of the machine-vision system.
FIG. 17A is a top view of the compartment and the elevator mechanisms below each of the inspection stations of the machine-vision system.
FIG. 17B is a side view of one of the compartment and the elevator mechanisms below an inspection station.
FIG. 18A is a top view of the inspection stations and the tray-transfer devices for moving trays between the various inspection stations, the pick and place stations, and the tray inverter or flipper mechanism.
FIG. 18B is a front view of one of the tray-transfer devices for moving trays between the various inspection stations, the pick and place stations and the tray inverter or flipper mechanism.
FIG. 19A is a side view of one tray inverter mechanism.
FIG. 19B is a front view of the tray inverter mechanism of FIG. 19A.
FIGS. 19C, 19D, 19E, 19F, 19G are front views of another tray inverter mechanism.
FIGS. 19H, 19I, 19J, 19K, 19L are side views of the tray inverter mechanism of FIGS. 19C-19G, respectively.
FIG. 20 shows picker for replacing devices.
FIG. 21 shows an acquired image showing various heights of a ball being inspected.